1. Field of the Invention
The present invention relates to apparatus, methods, and computer simulations highly suitable for treatment of benign prostatic hyperplasia (BPH) and, more particularly, to a unique catheter for microwave treatment of BPH to necrose prostatic tissue while protecting urethral tissue and computer simulations relating to the same.
2. Description of Prior Art
Benign prostatic hypertrophy or hyperplasia (BPH) is one of the most common medical problems experienced by men over 50 years old. Urinary tract obstruction due to prostatic hyperplasia has been recognized since the earliest days of medicine. Hyperplastic enlargement of the prostate gland, or enlargement due to abnormal but benign multiplication of the cells thereof, often leads to compression of the urethra thereby resulting in obstruction of the urinary tract. Common symptoms that develop from this condition may include more frequent urination, decrease in urinary flow, nocturia, pain, and discomfort. The incidence of BPH in men over 50 years of age is approximately 50 percent and increases to over 75 percent in men over 80 years of age. Symptoms of urinary obstruction occur most frequently between the ages of 65 and 70 when approximately 65 percent of men in the age group have prostatic enlargement.
When treatment by drug therapy is not sufficiently effective, surgical procedures for treating BPH are available but have potential side effects. General surgical risks apply such as anesthesia related morbidity, hemorrhage, coagulopathies, pulmonary emboli, electrolyte imbalance, and the like. Other problems that may occur from surgical correction include cardiac complications, bladder perforation, incontinence, infection, urethral or bladder neck stricture, retention of prostatic chips, and infertility. Due to the problems of surgery, many or even most patients delay treatment. However, the delay of treatment may lead to other complications including obstructive lesion in the prostate, chronic infection, and the like. Therefore it is unquestionable that a need exists for improved surgical or non-surgical methods for treating BPH.
Microwaves and other techniques have been used to necrose malignant, benign, and other types of cells and tissues including glandular and stromal nodules characteristic of benign prostate hyperplasia. However, problems encountered include a lack of focusing or direction of the energy thereby resulting in damage of healthy tissue.
The following patents disclose attempts to solve the above discussed difficult problems and related problems.
U.S. Pat. Nos. 5,904,709, issued May 18, 1999, to Arndt et al., and incorporated herein, discloses a method and apparatus for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to the monopole microwave radiator having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may be used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.
U.S. Pat. No. 5,843,144, issued Dec. 1, 1998, to Rudie et al., discloses a method for treating an individual with diseased prostatic tissue, such as benign prostatic hyperplasia, including inserting a catheter into a urethra to position a microwave antenna located within the catheter adjacent a prostatic region of the urethra. A microwave antenna is then driven within a power range for applying microwave energy substantially continuously to prostatic tissue to heat the prostatic tissue surrounding the microwave antenna at a temperature and for a time period sufficient to cause necrosis of the prostatic tissue.
U.S. Pat. No. 5,843,026, issued Dec. 1, 1998, to Edwards et al., discloses a method and apparatus for delivering controlled heat to perform ablation to treat the benign prosthetic hypertrophy or hyperplasia (BPH). According to the method and the apparatus, the energy is transferred directly into the tissue mass which is to be treated in such a manner as to provide tissue ablation without damage to surrounding tissues. Automatic shut-off occurs when any one of a number of surrounding areas to include the urethra or surrounding mass or the adjacent organs exceed predetermined safe temperature limits. The constant application of the radio frequency energy over a maintained determined time provides a safe procedure which avoids electrosurgical and other invasive operations while providing fast relief to BPH with a short recovery time. The procedure may be accomplished in a doctor""s office without the need for hospitalization or surgery.
U.S. Pat. No. 5,830,179, issued Nov. 3, 1998, to Mikus et al., discloses a stent system and method for use in the prostate gland. The stent is made of a shape memory alloy such as nitinol, and has a low temperature martensite state, with a martensite transition temperature below body temperature, and a high temperature austenite state, with an austenite transition temperature at or above body temperature, and a memorized shape in the high temperature austenite state which is a helical coil of diameter large enough to hold the prostatic urethra open. The stent is used to heat the prostate and is left in the prostatic urethra while the prostate heals. After the prostate is substantially healed, the stent is cooled to its martensite state and is easily removed from the urethra.
U.S. Pat. No. 5,800,486, issued Sep. 1, 1998, to Thome et al., discloses an intraurethral catheter which includes a microwave antenna and a cooling lumen structure substantially surrounding the antenna. A cooling balloon partially surrounds the cooling lumens on one side of the catheter adjacent the microwave antenna. The cooling balloon improves wall contact between the catheter and a wall of the urethra to improve cooling of the urethra. The cooling balloon communicates with the cooling lumen structure to permit circulation of cooling fluid through the cooling balloon.
U.S. Pat. No. 5,800,378, issued Sep. 1, 1998, to Edwards et al., discloses a medical probe device comprising a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and a stylet guide for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The total catheter assembly includes a stylet guide lumen communicating with the stylet port and a stylet positioned in said stylet guide lumen for longitudinal movement from the port through intervening tissue to target tissue. The stylet can be an electrical conductor enclosed within a non-conductive layer, the electrical conductor being a radio frequency electrode. Preferably, the non-conductive layer is a sleeve which is axially moveable on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue. The stylet can also be a microwave antenna. The catheter can include one or more inflatable balloons located adjacent to the stylet port for anchoring the catheter or dilation. Ultrasound transponders and temperature sensors can be attached to the probe end and/or stylet. The stylet guide can define a stylet path from an axial orientation in the catheter through a curved portion to a lateral orientation at the stylet port.
U.S. Pat. No. 5,755,754, issued May 26, 1998, to Rudie et al., discloses an intraurethral, Foley-type catheter shaft containing a microwave antenna capable of generating a cylindrically symmetrical thermal pattern, within which temperatures are capable of exceeding 45xc2x0 C. The antenna, which is positioned within the shaft, is surrounded by means within the shaft for absorbing thermal energy conducted by the tissue and asymmetrically absorbing electromagnetic energy emitted by the antennaxe2x80x94a greater amount of electromagnetic energy being absorbed on one side of the shaft. This asymmetrical absorption alters the thermal pattern generated by the microwave antenna, making it cylindrically asymmetrical, which effectively focuses microwave thermal therapy toward undesirous benign tumorous tissue growth of a prostate anterior and lateral to the urethra, and away from healthy tissue posterior to the urethra.
U.S. Pat. No. 5,733,315, issued Mar. 31, 1998, to Burdette et al., discloses an apparatus for applying thermal therapy to a prostate gland, comprising a support tube having a longitudinal central passageway, a power lead channeled through the longitudinal central passageway and an ultrasound crystal disposed around at least part of the support tube. The ultrasound crystal is coupled to the power lead which provides the power to energize the ultrasound crystal and generate ultrasound energy providing thermal therapy to the prostate gland. The ultrasound crystal further includes inactivated portions for reducing ultrasound energy directed to the rectal wall of the patient. A sealant is disposed in contact with the ultrasound crystal allowing vibration necessary for efficient ultrasound energy radiation for the thermal therapy to the prostate gland.
U.S. Pat. No. 5,720,718, issued Feb. 24, 1998, to Rosen et al., discloses a medical probe device comprising a catheter having a stylet guide housing with at least one stylet port in a side thereof and stylet guide means for directing a flexible stylet outward through at least one stylet port and through intervening tissue to targeted tissue. The stylet comprises an electrical central conductor which is enclosed within an insulating or dielectric sleeve surrounded by a conductive layer terminated by an antenna to selectively deliver microwave or radio frequency energy to target tissue. One embodiment includes the electrical conductor being enclosed within a non-conductive sleeve which itself is enclosed within a conductive sleeve in a coaxial cable arrangement to form a microwave transmission line terminated by an antenna. Another embodiment includes a resistive element near the distal end of the stylet which couples the center electrode to an outer conductor to generate joulian heat as electromagnetic energy is applied, such as an RF signal.
U.S. Pat. No. 5,643,335, issued Jul. 1, 1997, to Reid et al., discloses a system for treatment of benign prostatic hyperplasia within intraprostatic tissue surrounding a urethra. The system includes an intraurethral catheter having an intraurethral catheter shaft. An antenna is located within the catheter shaft for delivering heat to the intraprostatic tissue surrounding the urethra. Coolant fluid is circulated through a chamber located between the catheter shaft and the urethral wall.
U.S. Pat. No. 5,620,480, issued Apr. 15, 1997, to Eric N. Rudie, discloses a method for treating an individual with benign prostate hyperplasia. The method includes inserting a catheter into a urethra so as to position an energy emitting element located within the catheter adjacent a prostatic region of the urethra. A fluid is circulated within the catheter until the fluid stabilizes at a prechilled temperature. An energy emitting element is then energized sufficient to heat prostatic tissue surrounding the energy emitting element.
U.S. Pat. No. 5,599,294, issued Feb. 4, 1997, to Edwards et al., discloses a medical probe device comprising a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and guide means for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The stylet can be an electrical conductor enclosed within a non-conductive layer, the electrical conductor being a radio frequency electrode. Preferably, the non-conductive layer is a sleeve which is axially moveable on the electrical conductor to expose a selected portion of the electrical conductor surface in the target tissue. The stylet can also be a microwave antenna.
U.S. Pat. No. 5,575,811, issued Nov. 19, 1996, to Reid et al., discloses a system for treatment of benign prostatic hyperplasia within intraprostatic tissue surrounding a urethra. The system includes an intraurethral catheter having an intraurethral catheter shaft. An antenna is located within the catheter shaft for delivering heat to the intraprostatic tissue surrounding the urethra. Coolant fluid is circulated through a chamber located between the catheter shaft and the urethral wall.
U.S. Pat. No. 5,509,929, issued Apr. 23, 1996, to Hascoet et al., discloses a urethral probe having a front part and a rear part, and a microwave antenna connected to an external device for generating microwaves. The microwave antenna has its primary active heating part arranged in the urethral probe to be directed onto the prostatic tissue located at least at the level of the bladder neck in the working position. The urethral probe constitutes an essential element of a device for the therapeutic treatment of tissues by thermotherapy, more particularly tissues of the bladder of a human being.
U.S. Pat. No. 5,464,437, issued Nov. 7, 1995, to Reid et al., discloses a system for treatment of benign prostatic hyperplasia within intraprostatic tissue surrounding a urethra. The system includes an intraurethral catheter having an intraurethral catheter shaft. An antenna is located within the catheter shaft for delivering heat to the intraprostatic tissue surrounding the urethra. Coolant fluid is circulated through a chamber located between the catheter shaft and the urethral wall.
U.S. Pat. No. 5,413,588, issued May 9, 1995, to Rudie et al., discloses an intraurethral, Foley-type catheter shaft containing a microwave antenna capable of generating a cylindrically symmetrical thermal pattern, within which temperatures are capable of exceeding 45xc2x0 C. The antenna, which is positioned within the shaft, is surrounded by means within the shaft for absorbing thermal energy conducted by the tissue and asymmetrically absorbing electromagnetic energy emitted by the antennaxe2x80x94a greater amount of electromagnetic energy being absorbed on one side of the shaft. This asymmetrical absorption alters the thermal pattern generated by the microwave antenna, making it cylindrically asymmetrical, which effectively focuses microwave thermal therapy toward undesirous benign tumorous tissue growth of a prostate anterior and lateral to the urethra, and away from healthy tissue posterior to the urethra.
U.S. Pat. No. 5,366,490, issued Nov. 22, 1994, to Edwards et al., discloses a medical probe device comprising a catheter having a stylet guide housing with one or more stylet ports in a side wall thereof and guide means for directing a flexible stylet outward through the stylet port and through intervening tissue at a preselected, adjustable angle to a target tissue. The stylet can also be a microwave antenna.
U.S. Pat. No. 5,312,392, issued May 17, 1994, to Hofstetter et al., discloses a method of treating benign prostatic hyperplasia employing the steps of inserting a diffusing light guide into a prostrate lobe and providing laser power to the diffusing light guide in order to necrose surrounding tissue. The diffusing light guide can be inserted into the central or lateral prostrate lobes by inserting a needle and a trocar transperineally into the middle of the lateral lobe, removing the trocar, inserting the diffusing light guide, and monitoring the position of the needle, trocar, and diffusing light guide using ultrasound. The diffusing light guide can also be inserted into the central or lateral prostrate lobes transurethrally and positioned with the aid of an urethroscope.
U.S. Pat. No. 4,967,765, issued Nov. 6, 1990, to Turner et al., discloses a urethral inserted applicator for prostate hyperthermia including a multi-tube, balloon type catheter. The catheter includes first and second closed end fluid dry tubes, respectively, for a helical coil antenna type applicator, and a microwave type temperature sensor for measuring the temperature of the prostate tissue, and an open fluid receiving tube. A microwave generator supplies electromagnetic energy to the applicator. A comparator is connected to the temperature sensor and a temperature reference potentiometer for comparing the actual tissue temperature level with a desired temperature level and outputting control signals to the microwave generator for controlling the output to the applicator. The coil type applicator is an elongated coil having a tip end connected to the center conductor of a coaxial cable and an opposite end connected to the outer conductor of the coaxial cable. A sheet or sheath of insulation material covers the coil antenna for insulating the coil from the tissue and the thickness of the sheet may be varied to provide uniform tissue heating along the length of the coil. The balloon of the catheter engages the body""s bladder to position the applicator properly during the treatment.
The above cited prior art does not provide an easily fabricated catheter that may be fabricated with variations useful for individual patients, a computer simulation to predict the effect of procedural techniques, and a relatively quick procedure that may be performed in minutes to necrose prostatic tissue while protecting healthy tissue. Consequently, there is a strong need for improved treatment techniques that accurately pinpoint and necrose selected prostatic tissue while protecting the urethra and other healthy structures by cooling and by selectively directing microwave radiation. Those skilled in the art have long sought and will appreciate the present invention that addresses these and other problems.
The present invention provides a procedure, apparatus, and computer simulation for treating benign prostatic hyperplasia (BPH). The computer simulation may be used to predict a temperature profile that will be produced given the various inputs related thereto. Alternatively, it may be used to provide suitable procedure variables such as frequency, time duration, and power level, given the desired temperature profile. The procedure has a treatment time of only a few minutes and is designed to prevent damage to healthy tissue such as the urethra. The antenna may be made directional to protect structures such as the colon and structures such as ducts radially outside the urethra. For purposes of the present invention, a catheter is assumed to include a probe, cannula or other medical device for insertion into the body such as into the urethra for treatment purposes.
For this purpose, a transcatheter microwave antenna is disclosed that comprises a catheter preferably formed from a microwave transmission line having first and second opposing ends. The first end may be adapted for connection to a microwave power source. The microwave transmission line preferably has a center conductor and an outer conductor. A microwave antenna is disposed on the second end of the microwave antenna. A layer of fusion material is disposed radially outward of the microwave antenna. The fusion material is operable to be in a first physical state prior to operation of the microwave antenna. The fusion material is alterable to a second physical state from the first physical state to provide heat of fusion cooling adjacent the catheter during operation of the microwave antenna. In a preferred embodiment, the fusion material may be in a solid physical state prior to operation of the microwave antenna and is operable for melting to a liquid state during operation of the microwave antenna so as to provide cooling radially outward from the catheter. The fusion material in the solid state is substantially flexible. The fusion material is substantially transparent to microwave radiation so as to absorb little energy directly from the microwave radiation. In one embodiment, the fusion material has a melting point in the range of from approximately eighty to one hundred degrees Fahrenheit.
Electrical insulating material is preferably provided between the center conductor and the outer conductor. The microwave antenna may be disposed within the electrical insulating material in a preferred embodiment. An outer sheath preferably but not necessarily surrounds the fusion material. The layer of fusion material is provided in surrounding relationship to the microwave antenna. In one embodiment, the fusion material is comprised of a crystalline material. In another embodiment, the fusion material is comprised of powdered material. The fusion material, in one embodiment, may be comprised of either dibasic sodium phosphate or phosphonium chloride.
Preferably a tubular conductor acts as an attenuator of microwaves and may be mounted at or near a surface of the catheter and may be axially positioned on the catheter adjacent the microwave antenna. In one embodiment of the invention, material is provided for absorbing microwave heat energy on one side of the microwave antenna so as to make the microwave antenna directional.
A method of constructing a transcatheter microwave antenna may include providing a coaxial cable with a center conductor and an outer conductor. The coaxial cable is adapted for connection to a microwave power source. A microwave antenna at one end of the coaxial cable and a layer of fusion material is provided adjacent the microwave antenna. The fusion material is operable to be in a first physical state prior to operation of the microwave antenna and may be alterable to a second physical state from the first physical state to provide heat of fusion cooling adjacent the catheter during operation of the microwave antenna. The fusion material is selected to have a melting temperature in the range from about eighty to one hundred degrees Fahrenheit.
A method for selective thermal necrosing of a tissue to be treated while limiting thermal damage to a protected tissue that comprises positioning an energy radiator adjacent to heat the tissue to be treated such that the protected tissue is between the tissue to be treated and the energy radiator. A layer of fusion material is positioned between the energy radiator and the protected tissue such that convection transfer of energy may occur between the protected tissue and the layer of fusion material. Energy is radiated from the energy radiator to heat the tissue to be treated. The temperature rise in the protected tissue is limited by convection transfer of energy between the protected tissue and the fusion material. The temperature rise in the fusion material is limited by changing the fusion material from a first physical state to a second physical state due to the convection transfer of energy between the protected tissue and the fusion material. The fusion material preferably has a melting point below body temperature. The energy radiator may be controlled so as to direct energy from the energy radiator in one or more selected directions toward the tissue to be treated. This may be accomplished by positioning the energy absorbing material adjacent the energy radiator to absorb energy from the energy radiator. A frequency of operation may be selected based on a distance of the energy radiator to the tissue to be treated so as to focus energy to the tissue to be treated.
Thus, in operation a method for selective thermal ablation of a tissue to be treated is provided that limits thermal damage to protected tissues and comprises positioning fusion material adjacent the protected tissue to permit convection transfer of energy between the fusion material and the protected tissue, the fusion material preferably has a melting point lower than body temperature. Energy is radiated through the fusion material and through the protected tissue and into the tissue to be treated. Microwaves along the outside of the catheter are attenuated with a tubular conductor. The microwave antenna may be adjusted so that the radiation points deposit energy at a selected distance of the tissue to be treated from the microwave antenna.
A computer program is provided for simulating treatment in biological tissue which comprises providing at least one antenna characteristic for the microwave antenna. At least one tissue characteristic is provided of the tissue into which microwave energy is to be deposited. At least one cooling characteristic of cooling substances through which microwaves are transmitted is provided. A frequency of operation and a power level may be provided. A delivery time for the microwave energy may be provided. A temperature profile produced within the biological tissue may be determined. The temperature versus distance radially outward from the microwave antenna may be displayed graphically in some manner. The changes in the temperature profile with time may be displayed. The computer program may also include a characteristic of absorption material for absorbing the microwave energy in at least one direction so as to alter the temperature profile accordingly.
One object of the present invention is to provide an improved instrument and method for necrosing certain tissue while protecting other tissue.
Another object of the present invention is to provide an improved instrument, method, and computer simulation for treating benign prostatic hyperplasia.
Yet another objective of the present invention is to provide a treatment that necroses prostatic tissue but protects other tissue such as the urethra.
Any listed objects, features, and advantages are not intended to limit the invention or claims in any conceivable manner but are intended merely to be informative of some of the objects, features, and advantages of the present invention. In fact, these and yet other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims.